Email is a method for transmitting data like text, photos, and files between computers over the internet. During the 1960s and 1970s, companies in the US began using email between terminals attached to their systems, even before the internet existed. As companies connected their systems worldwide in the early 1990s, email became popular for employees to communicate globally. Today, email users can create messages and attach files using commercial programs, specifying recipient addresses and domains in standard formats like name@organization.country to send messages easily around the world.